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Pad knock-back questions

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#1
Sphinx

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I've never really experienced pad knock-back till last weekend at VIR.  Obviously, I know what I need to do to reset them and will now incorporate that as part of my driving routine.  But a couple of questions more on the maintenance side -

 

1)  Is this typically an issue with the front or rear pads or both?

2)  at what pad depth do you simply get rid of the pads to avoid this problem (as compared to leaving them on to get maximum usage)?

 

Before last weekend, I put on fresh fronts but rears were three weekends old.  But as the weekend wore on, I felt that I was losing braking confidence.  We bled brakes just to be sure and that helped minimally.



#2
Steve Scheifler

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Crickets :(

My answers reflect only our experience and most of that before the really bad gators were added at tracks we frequented, but hopefully other will chime in.

Back before we started running rears with the auto-adjuster removed we experienced only occasional and relatively minor knockback, presumably on the fronts. But we were running mostly tracks without a lot of rumbles/gators. Later tracks like Blackhawk added rough gators and Road America made theirs much more severe, and then knockback became a big issue. But around that time we also started running gutted rears, so I’m not really inclined to assume which end if either is more prone to the problem.

At some tracks we still never give it a thought, and so at those we run the pads down thinner. At others it can be catastrophic if forgotten, and significantly reduced with newer pads so we’d start the weekend on new or nearly new and save the partials for other tracks. You can also run additional shims to increase overall thickness but after buying some to experiment with it seemed like too much hassle.
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Bona fide - A bonafide Spec Miata driver

#3
TylerQuance

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We <3 pad knock back. Dragging brakes = slow miata

#4
Sphinx

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So, took apart the rear brakes to swap new pads and saw that that the upper caliper pin was badly loose.  Curious as to whether that would have contributed to a longish pedal and my lack of confidence in the brakes.   Thoughts?



#5
RWP80000

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So, took apart the rear brakes to swap new pads and saw that that the upper caliper pin was badly loose.  Curious as to whether that would have contributed to a longish pedal and my lack of confidence in the brakes.   Thoughts?

I would say with certainty that a loose upper caliper pin would contribute to increased levels of caliper movement which would likely result even greater caliper piston "knock back".  This is also true for those who do not run the stainless caliper bracket clips and brake pad separating springs as the excessive clearance of the pads rattleing around also contributes excessive motion not to mention contributing to uneven pad wear.

 

Rich Powers


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#6
Sphinx

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I would say with certainty that a loose upper caliper pin would contribute to increased levels of caliper movement which would likely result even greater caliper piston "knock back".  This is also true for those who do not run the stainless caliper bracket clips and brake pad separating springs as the excessive clearance of the pads rattleing around also contributes excessive motion not to mention contributing to uneven pad wear.

 

Rich Powers

 

Thanks Rich.  Yep, my car didn't have rear springs from the prior owner.  Pad wear is even so far, but I'm picking up some rear hardware to mitigate the pedal travel, even if negligibly.  






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